1. Field
This disclosure relates to a rechargeable lithium battery including a negative active material.
2. Description of the Related Art
Lithium rechargeable batteries have recently drawn attention as a power source for small portable electronic devices. They use an organic electrolyte solution to thereby have discharge voltage that is twice higher than that of a conventional battery using an alkali aqueous solution, and accordingly, the lithium rechargeable batteries have high energy density.
As for positive active materials of a rechargeable lithium battery, there has been research on a lithium-transition element composite oxide that can intercalate lithium such as LiCoO2, LiMn2O4, LiNi1−xCoxO2 (0<x<1), etc.
On the other hand, negative active materials of a rechargeable lithium battery have included various carbon-based materials such as artificial graphite, natural graphite, and hard carbon, which can all intercalate and deintercalate lithium ions. Since graphite among the carbon-based materials has a low discharge potential relative to lithium of +0.2V, a battery using the graphite as a negative active material has a high discharge potential (ranging) at 3.6V or 3.8V or between 3.6V and 3.8V and excellent energy density. Furthermore, the graphite guarantees a long cycle life for a battery due to its outstanding reversibility. However, a graphite active material has low material density (theoretical density of 2.2 g/cc and actual density of 1.1 to 1.7 g/cc) and consequently low capacity in terms of energy density per unit volume when the graphite is used as a negative active material. Further, it has swelling or capacity reduction problems, because the graphite is likely to react with an organic electrolyte during charging and discharging.
In order to solve these problems, oxide negative active materials such as tin oxide, lithium vanadium-based oxide, and the like have been developed. However, oxide negative electrodes do not provide a satisfying battery performance and thus, have been continuously researched.